The introduction of new techniques for evaluating fetal status, particularly fetuses at theoretical risk for hypoxic ischemic encephalopathy, requires the most rigorous evaluation before widespread clinical deployment. The considerations extend beyond clinical value to the significant medicolegal implications of a failure to predict or ascertain compromise. The attitudes to clinical Doppler velocimetry have been shaped to a large extent by these practical concerns and the initial skepticism, which is a necessary component of scientific rigor. Available data strongly indicate, however, that in competent hands umbilical artery Doppler im-proves the clinical management of IUGR pregnancies. Failure to use Doppler may have the undesirable effect of increasing the risk of adverse outcome in the growth-restricted fetus. There is also strong evidence of benefit in the management of the Rh isoimmunization. Although numerous other clinical applications are on the horizon, much more information is needed to determine objectively the benefits and risks of these newer applications.